I have a home built AR that runs 55 grain all day long, but will only run 77 grain until it warms up. It then starts stovepiping every 5 rounds or so and the next round is usually a light primer strike after that. Can’t figure it out, it did this on both the Hornady projectile and the Sierra Matchking projectiles that I tried today. First mag was perfect and then it warmed up and started getting the malfunctions. That being said, the barrel really likes the projectiles, so I would like to get it working. Both projectile types were shot from brand new magpul pmags, fresh out of the wrapper, to make sure that they weren’t the issue. Here was the third mag results minus the shots that light primer striked.
You can see why I want these rounds to work, this was at 25 yards, with a red dot and magnifier, at the longest bay they had available today. Edit: all parts were PSA, from a Let’s Go Brandon lower and parts kit, to the already built upper I bought.
with the heavier rounds are you noticing a bit more residue on the bolt when you clean it? When shooting heavier stuff in mine and it starts to act up I give it a little extra oil on the bolt and it starts to run better. I think the extra blow back from the heavier bullet moving slower through the barrel is getting the action gummier and a bit more wet is what it needs.
Consensus in another group was try a H2 buffer, so I ordered one. I intend on trying IMI ammo also as I have had great luck with their 55 grain, just haven’t tried the Razorcore yet.
Ok, I put in the H2 buffer and that almost completely eliminated the stovepipes (had one) but the light strikes got worse. I had a professional take a look and shoot it and he determined it was the trigger. Changed the trigger to a Rise Armament single stage and will try again tomorrow. The AAC ammo shoots fine, but appears to be really dirty.
Range trip today was a short one, just to see what the new trigger did for me. In 60 rounds fired of IMI 77 grain Razorcore, I had no light strikes and one stovepipe. While I would like to get rid of the stovepipes all together, it’s definitely a step in the right direction. Here is the target at 25 yards, I had one “flyer” in the seven ring, but otherwise pretty good group.
